1. Field of the Invention
The present invention relates to a lamp unit, more specifically to a lamp unit having a lamp holder to hold a lamp, a lamp attachment for holding the lamp holder and being attached to an object, and a transparent cover attached to the lamp attachment and covering a front side of the lamp attachment and the lamp holder.
2. Description of the Related Art
FIGS. 6A and 6B show a conventional room lamp as a lamp unit to be attached to a roof of a vehicle. Refer to JP-2004-203344,A. FIG. 6A is a front view of the room lamp and FIG. 6B is a front perspective view thereof with a cover lens 30 being removed.
As shown in FIGS. 6A and 6B, the room lamp includes a lamp holder 10 to hold a lamp L, a lamp bezel (lamp attachment) 20 for holding the lamp holder 10 and being attached to the roof of the vehicle, and the cover lens (transparent cover) 30 attached to the lamp bezel 20 and covering all over a front side of the lamp bezel 20 and the lamp holder 10.
The lamp bezel 20 has a lamp window 21 in the center and holds the lamp holder 10 for the lamp L to be exposed to the front side thereof through the lamp window 21. The lamp bezel 20 has attachment portions 24, such as engaging claws, to be engaged with engaged holes (not shown) disposed at the roof of the vehicle, at a rear surface thereof. The lamp bezel 20 has a plurality of through-holes 25 therein. The plurality of the through-holes 25 are formed when the attachment portions 24 are formed by die-cutting the lamp bezel 20. Screw holes also become the through-holes 25.
As shown in FIG. 6B, the lamp bezel 20 has sliding grooves 23 in a longitudinal direction thereof. A sliding member 40 is slidably engaged with the sliding grooves 23 at the front side of the lamp bezel 20. A knob 41 is disposed at a front side of the sliding member 40 and exposed to outside from a front opening 31 of the cover lens 30. The sliding member 40 is slid by means of the knob 41 so as to turn on and off the lamp L.
A whole area of a rear surface of the cover lens 30 is embossed so as that the lamp holder 10, the through-holes 25 formed in the lamp bezel 20, and the sliding grooves 23 are not visible from a front side of the room lamp, i.e., the cover lens 30 appears cloudy.
Then, the cover lens 30 loses transparency and appearance design. In the conventional lamp unit, the cover lens 30 is embossed entirely and has a uniform light transmittance. However, when the cover lens 30 is embossed thinly in order to increase the light transmittance and brightness, the lamp holder 10 or through-holes 25 formed in the lamp bezel 20 becomes visible through the cover lens 30. On the contrary, when the cover lens 30 is embossed densely for the lamp holder 10 or the through-holes 25 to be invisible, the brightness is reduced.
The uniform light transmittance of the conventional cover lens 30 results in that the brightness of the cover lens 30 is high at an area close to the lamp L and becomes lower with a distance from the lamp L.